1. Field of the Invention
The present invention relates generally to a digital camera module with an auto-focusing function and, more particularly, to a small-sized digital camera module with an auto-focusing function and to a portable electronic device, such as a mobile phone or a Personal Digital Assistant (PDA), having such a camera module mounted therein.
2. Discussion of the Related Art
Recently, with the development of wireless communication technologies, there are many cases where digital cameras are mounted in mobile phones or PDAs.
Generally, digital cameras are image recording media capable of photographing a plurality of still images without using film. Such a digital camera typically uses an image pickup device, which is a kind of semiconductor device, such as a Charge Coupled Device (CCD) or Complementary Metal Oxide Semiconductor (CMOS). In the digital camera, an object image formed on the image pickup device through a lens is converted into an electrical signal by the image pickup device, and the electrical signal is stored as a digital signal, e.g., in the camera unit or in a mobile phone or PDA in which the digital camera is mounted.
Since the digital camera is desirably mounted in small mobile phones or PDAs, a fixed focus lens module is usually used to facilitate mounting thereof within a small phone or PDA. However, images photographed by a digital camera module with a fixed focus lens module tend to be poor in quality. It is partly due to the fixed focus lens, which is incapable of adjusting focal length to make a clearer image.
A kind of conventional digital camera with a focusing function usually uses an actuator, such as step motor, to drive the lens module, such as disclosed in Taiwan Patent No. 88200669. Referring to FIG. 3 (Prior Art), a focusing adjusting apparatus includes an inner housing 60, a lens 62, a circular gear 64, and a step motor 66. The lens 62 and the step motor 66 are received in the inner housing 60. One end of the step motor 66 is connected with a driving gear 662. The driving gear 662 drives the circular gear 64 to rotate, which makes the lens 62 located in the circular gear 64 move. However, the focusing adjusting apparatus using such a step motor is relatively large in volume and consumes a substantial amount of power, especially relative to the amount of power that can be stored in the typical battery system of a mobile phone or PDA. As such, a step motor is not suitable to be used in mobile phone or PDA, which needs to be small and power saving.
Another kind of conventional digital camera with a focusing function usually uses an actuator such as coil motor to drive the camera lens disclosed in U.S. Patent Application No. 2004016587, published Aug. 26, 2004. Referring to FIG. 4 (Prior Art), a drive source of a camera lens is disclosed. The camera lens includes a camera lens mount 70, a telescopic lens 72, a coil stator 74, and a magnetic ring rotor 76. The coil stator 74 and the magnetic ring rotor 76 cooperate with each other to drive the telescopic lens 72. The inside of the camera lens mount 70 is built with the coil stator 74 to place the magnetic ring rotor 76 inside a designated space 742. The outside of the telescopic lens 72 is designed with an external thread member 722 to allow it to be screwed on an internal thread 764 on the inside of a spindle 762 of the magnetic ring rotor 76. The magnetic ring rotor 76 rotates under the reaction induced by the coil stator 74, and the internal thread 764 of the spindle 762 drives the external thread 722 of the telescopic lens 72 for telescopic motion. However, the presence of the magnetic rotor 76 increases the weight of the digital camera lens. Further, the combination of the coil stator 74, the magnetic ring rotor 76, the external thread member 722, and the telescopic lens 72, together, will occupy a relatively large volume, and the adjustment of such a combination will consume a substantial amount of power, especially relative to the amount of power that can be stored in the typical battery system of a mobile phone or PDA.
What is needed, therefore, is a digital camera module with an auto-focusing function, which satisfies the needs for performance enhancement, downsizing, and power saving.